Resinous composition containing polyester resin, for coating use

ABSTRACT

Resinous composition for use in coating comprising a hexahydrophthalic acid or anhydride thereof whose acidic groups are capable of developing a resinous acid value and etherified aminoformaldehyde resin. This resinous composition is characterized by possessing all the advantages of oil-free polyester resin compositions such as good weather resistance mechanical properties in the coating, interlaminar adhesion and the like, and furthermore the composition inter alia, has excellent weather resistance because of its modification with saturated alicyclic acids and the curing properties are enhanced because of the control of the acidic groups which develops a resinous acid value. The invention also provides a coating composition, containing as a vehicle, the aforementioned resinous composition.

This application is a continuation-in-part of application Ser. No. 782,613 filed Oct. 1, 1985, which is a continuation of application Ser. No. 608,694, filed May 2, 1984, both applications being now abandoned.

FIELD OF THE INVENTION

The present invention relates to resinous composition for coating use and more specifically a coating composition which is useful as a top coat for automobile bodies and the like and is excellent in weather resistance, mechanical properties of the film, interlaminar adhesion and particularly in the curability thereof.

BACKGROUND OF THE INVENTION

Recently, as a top coat for automobile bodies and the like, has been welcomed a coating composition which is excellent in weather resistance, mechanical properties of the film, and interlaminar adhesion and oil-free polyester/amino aldehyde reinous system is now receiving increased attention. However, this type of coating composition is apt to result, in considerable cising and hence is difficult to make produce a uniform coating, since a coating having an inferior glossy surface is formed which shows poor compatibility with the amino resin, and for these reasons, it is difficult to apply such coatings to automobile bodies and the like. Under the circumstances, as an attempt of overcoming the defect possessed by heretofore known oil-free polyester/amino resins coating compositions, as mentioned above, while maintaining the advantages thereof, a proposal has been made to use a larger quantity of a saturated alicyclic polycarboxylic acid or a combination of an aromatic polycarboxylic acid and a saturated alicyclic polycarboxylic acid as an acid component of a oil free polyester resin (Japanese Patent Application Kokai No. 20068/81). The use of such saturated alicyclic acid modified polyester resin (hereinafter merely called a modified polyester resin), however, serves only to some extent to improve the occurence of cissing, dim gloss and poor compatibility with said amino resin, and therefore, it is difficult to overcome the aforementioned shortcomings. Moreover, a new problem of insufficient curing occurs due to the modification with said saturated alicyclic acid, making it very difficult to put the resin in practical use. Therefore, an object of the present invention is to provide a coating composition which retains the excellent qualities of a known oil-free polyester/amino resin system, but which is free from the defects of insufficient curing inevitably produced by the use of such modified polyester resin, but which still exhibits excellent gloss and weather resistance properties. According to the studies of the present inventors, it has been found that the employment of saturated alicyclic polycarboxylic acid as a part of said acid component of polyester resin is indeed very effective for improving the weather resistance of the coating, but when the resin is mixed with a melamine resin and a cured film formed, it will cause the problem of reduced initial gloss and inferior curing and the inclusion of an aromatic polycarboxylic acid component is indeed of advantage in obtaining a film with improved gloss and curing properties, however, barely results in a film having advanced weather resistance. The inventors also have found that even if both a saturated alicyclic polycarboxyl acid and an aromatic polycarboxylic acid are used together for the purpose of obtaining a resinous film with excellent weather resistance, gloss and curing properties, this cannot always be achieved. This is because the reactivity of the saturated alicylic acid is rather poor, the aromatic polycarboxylic acid is more quickly incorporated into the polyester chain and the carboxyl groups contribute to the development of resinous acid values which may be occupied, in substance, by the alicyclic carboxylic acid with low dissociation in a non-aqueous medium, thereby resulting in resinous product with weak acidity. Thus, the present objectives of producing a resin with improved curing properties and yet possessing the capablity of producing a film with excellent weather resistance cannot be attained. In order to attain the objective of the present invention, it is essential that in addition to modifying the polyester with a saturated alicyclic acid (for improving the weather resistance), the type of carboxyl groups contributing to the development of resinous acid value must be controlled and at least part of said groups should be composed of aromatic polycarboxylic acids which are believed to be effective for improving the gloss and curing properties. The present invention has been made on the basis of these findings.

SUMMARY OF THE INVENTION

According to the invention, there is provided a resinous composition for coating use, which comprises 60 to 90% by weight of a polyester resin and 40 to 10% by weight of an amino-form-aldehyde resin etherified with a monohydric alcohol having 1 to 4 carbon atoms.

The resinous composition used in the coating compositions of the present invention is comprised of 60 to 90% by weight of an acid controlled modified polyester resin and 40 to 10% by weight of an aminoformaldehyde resin etherified with a monohydric alcohol having 1 to 4 carbon atoms, said polyester resin being composed of

(1) an alcohol component consisting of

(A) 20 to 64% by weight of at least one diol selected from the group consisting of neopentyl glycol and hydroxy pivalic acid neopentyl glycol ester,

(B) 14 to 34% by weight of a triol and

(C) 0 to 66% by weight of other polyhydric alcohol than said (A) and (B), and

(2) an acid component consisting of

(D) a mole % of saturated alicyclic polycarboxylic acid,

(E) b mole % of polycarboxylic acid which will give, at a state capable of developing resinous acid value, a titration midpoint potential in non-aqueous potentiometric titration of more than -350 mV, and

(F) c mole % of at least one acid selected from the group consisting of polycarboxylic acids other than said (D) and (E), and monocarboxylic acid,

wherein a is 10 to 80 and b+c is 90 to 20, 10 to 100 mole % of the carboxyl groups capable of developing resinous acid value of the polyester resin being derived from said (E) acid.

In the present specification and claims, the term "at the state capable of developing resinous acid value" shall mean a "carboxylic acid incorporated in a polyester resin as the sole acid component, whose carboxyl group still remains in a free form and is capable of developing a resinous acid value", and the term "carboxyl groups contributive to the development of acid value" means "carboxyl groups remaining in the final resin in free form which contribute to the development of the acid value of the polyester resin". The term "polyester resin" shall include both oil-free polyester and alkyd resins, and the term "titration midpoint potential" has the meaning stated by Douglas B. Bruss etal in Anal. Chem. 29, 232-235 (1957). Incidentally, in the instant specification, the term "acid controlled, modified" means the polyester resin, defined by the percent of carboxyl groups which contributes to the deveopment of the resinous acid value derived from the particular acid and the defined % of the total acid component occupied by the particular acid.

BRIEF EXPLANATION OF THE DRAWING

FIG. 1 shows a non-aqueous potentiometric titration curve of a polyester prepolymer A-1 (2) and of an acid controlled modified polyester resinous solution A (1) obtained in Example 1, wherein the ordinate axis indicates the electric potential and the transverse axis the titer measured by using an n-tetrabutyl ammonium hydroxide as a titration reagent.

PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the invention shall be explained hereinunder.

The acid controlled modified polyeser resin used in the present invention is characterized by a particular combination of acid components consisting of

(A) the a mole % of the hexahydrophthalic acid and anhydride thereof,

(B) the b mole % of polycarboxylic acid whose titration midpoint potential in the non-aqueous potentiometric titration, at the state of being capable of developing a resinous acid value, is more than -350 mV, and

(C) the c mole % of the other poly and/or mono carboxylic acid, wherein ##EQU1## Such polyester resin may be, as stated in Japanese patent application No. 154209/82, filed on Sept. 3, 1982 by the same applicant, preferably and advantageously prepared by the combination steps of reacting an acid mixture of (a) mole of (A) acid, (b-b₁) mole of (B) acid, and (C) mole of (C) acid, with a polyhydric alcohol to obtain a polyester prepolymer havng a resinous acid value of M, in which ##EQU2## and subjecting thus obtained prepolymer to an esterification with a b₁ mole of (B) acid, thereby obtaining a resinous product having an acid value of N.

In the abovesaid statement, b₁ is equal to or less than the b mole and denotes the amounts of (B) to be charged in a later stage and determined by the following equation: ##EQU3## wherein N stands for the resinous acid value of the final product (mg of KOH required for the neutralization of 1 g of resinous solid matter); W is the weight of the polyester resin; f is the number of functional groups possessed by (B); P is the reaction percentage (%) of (B) at the later charging stage; x is the mole % of (B) to be incorporated as carboxylic groups capable of exhibiting a resinous acid value and determined in a range of

    10≦×≦100

Briefly speaking, said method is characterized, in that the preparation of the acid controlled modified polyester resin, by first introducing a less reactive alicyclic acid ester into the polyester chain, following esterification with an amount of a later charged polycarboxylic acid (B) which has a considerably strong acidity, thereby obtaining a polyester in which the particular % of the carboxyl groups capable of exhibiting the resinous acid value are occupied by those of said (B) acid.

Examples of polycarboxylic acids showing the titration midpoint potential of more than -350 mV at the stage of being capable of developing resinous acid values may include aromatic polycarboxylic acids as phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic anhydride, pyromellitic anhydride and the like. Such polycarboxylic acid per se will, in general, will exhibit when an electric potential-TBAH titer curve is formed from the test results of a non-aqueous potentiometric titration, a curve having multi-stage inflection points, and however, when incorporated in polyester chain. When, however, at least one of the carboxyl groups remain in a free state the corresponding curve will exhibit a diminished number of inflection points, accordingly.

At the stage of being incorporated in the polyester chain, if a polycarboxylic acid is possessed of such acid strength that the aforesaid titration midpoint potential is more than -350 mV, then such a member may advantageously be used for the object of the present invention.

As the acid components, other poly-and/or monocarboxylic acids may be present, if desired.

Such acids may be any of the members customarily used as the acid component of polyester rein, including aliphatic or partially saturated alicyclic acids like succinic acid and its anhydride, adipid acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, maleic anhydride, fumaric acid, itaconic acid and the like. Furthermore, monocarboxylic acids such as benzoic acid, p-t-butyl benzoic acid and the like may be added for the purpose of regulating the molecular weight of the resin.

The polyhydric alcohol component to be reacted with said acid mixture is composed of a diol selected from neopentyl glycol and hydroxy pivalic acid neopentyl glycol ester, a triol such as trimethylol propane and trimethylol ethane, and an optional polyhydric alcohol other than said diols and triols. Examples of such optional polyhydric alcohols are alcohols selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol 2,3-butylene glycol, 1,4-butylene glycol, 1,6-hexane diol, 1,5-pentane diol, 2,5-hexane diol, glycerine, pentaerythritol, diglycerine, sorbitol, and 1,4-cyclohexane dimethanol.

One or more than two of said members may satisfactorily be used. As already stated, in said acid controlled modified polyester resin, 10-80 mole % of the total acid components should be occupied by said hexahydrophthalic acid or anhydride thereof (A) and moreover, 10-100 mole % of the carboxyl groups which develop a resinous acid value must be derived from the aforesaid polycarboxylic acid (B). Such acid control is essential. This is because, if the content of the hexahydrophthalic acid or anhydride thereof is less than 10 mole % of the total acid components, there is a tendency for the weather resistance not be improved, whereas if it exceeds the upper limit of 80 mole %, the chemical resistance be lowered. As the ratio of carboxylic groups responsible for the development of the resinous acid value, if the amount of said polycarboxylic acid having the specified acid strength is less than 10 mole %, then there is a general trend towards imparting insufficient gloss and curing properties and hence, the object of the present invention cannot be attained. In the actual preparation of the present acid controlled modified polyester resin, a polyester prepolymer is first prepared from an acid mixture of the (A) acid, the (C) acid (polycarboxylic and/or monocarboxylic acid) and, if desired, part of the (B) acid, and the polyhydric alcohol component, then the total amount or the remaining amounts of the (B) acid are added in later stage and esterification is continued to obtain the acid controlled modified polyester resin.

The amounts of polycarboxylic acid (B) used in the first step and in the second step reactions may be varied with the number of functional groups (f) in the polycarboxylic acid (B), the resinous acid value (N), the resin weight (W), the desired mole % (x) of carboxyl groups derived from said polycarboxylic acid (B) in the total carboxyl groups capable of developing a resinous acid value and the reaction rate (P) of the polycarboxylic acid (B) to be charged in the later stage. They are, however, determined as follows: That is, the amount of (B) to be charged in later stage (b₁ mole) is first determined by the aforesaid equation, and the amount of (B) to be used in the first step is then determined as the difference between the designated b mole and said b₁ mole. Incidentally, the reaction percentage % (P) of the polycarboxylic acid (B) to be charged in a later stage refers to the percentage of carboxyl groups in (B) added in later stage are to be reacted to ensure that the polycarboxylic acid is definitely incorporated into the polyester chain by esterification. This value is, for example, more than 50% in the case of a dicarboxylic acid, such as phthalic anhydride, and more that about 34% in the case of a tricarboxylic acid, such as trimellitic acid.

The esterification reaction between the polycarboxylic acid and the polyhydric alcohol may be carried out in a conventional way and no particular operational procedures are required. In a preferred embodiment, the reaction in the first step for obtaining the polyester prepolymer may be continued to a resinous acid value of 1-135, and the second step reaction to an acid value of 1-150. In regard to the number average molecular weight of the resin, it may satisfactorily be selected in a molecular weight range of the conventional polyester resins for coating use. In this way, there is provided an acid controlled modified polyester resin, 10 to 80 mole % of a the acid component being composed of saturated alicyclic polycarboxylic acid and 10 to 100 mole % of the carboxyl groups exhibiting an resinous acid value being derived from the polycarboxylic acid (B), whose titration midpoint potential in a non-aqueous potentiometric titration at the stage of being capable of developing resinous acid value, is more than-350 mV.

In the present invention, the abovesaid acid controlled modified polyester resin is used together with an aminoformaldehyde resin etherified with a monohydric alcohol having 1 to 4 carbon atoms, as, for example, a melamine resin, a guanamine resin, a urea resin and the like. The compounding ratio of these acid-controlled modified polyester resins and amino resin may be, in general, freely selected, in terms of solid weight ratio, to be in a range of 60 to 90% by weight of the former and 40 to 10% by weight of the latter. The most preferable range, however, is 70 to 80% by weight of the former and 30 to 20% by weight of the latter.

Thus, the present composition has the characteristics of an oil-free polyester coating composition, i.e. it possesses excellent weather resistance, interlaminar adhesion, mechanical properties of the coating and the like. Moreover, since the carboxyl groups capable of developing a resinous acid value of for the modified polyester resin are controlled in kind and the curing reaction with an amino resin proceeds quite smoothly because of the strong acidity, the composition exhibits improved curing properties and hence is very useful as a top coat for automobile bodies and the like.

The invention shall be now more fully explained in the following Examples. Unless otherwise being stated, all part and % are by weight.

EXAMPLE 1

Preparation of resinous composition containing acid controlled modified polyester resin, wherein 50 mole % of acid component is hexahydrophthalic anhydride and 75 mole % of the carboxyl groups capable of exhibiting resinous acid value of 8 are derived from isophthalic acid. Composition of acid controlled modified polyester resin A:

    ______________________________________                                         hexahydrophthalic anhydride                                                                      77.4     parts (0.5 mole)                                    isophthalic acid  66.48    parts (0.4 mole)                                    adipic acid       14.62    parts (0.1 mole)                                    trimethylolpropane                                                                               25.61    parts                                               neopentylglycol   52.67    parts                                               1,6-hexanediol    55.40    parts                                                                 292.18   parts                                               ______________________________________                                    

Calculation of isophthalic acid to be charged in later stage:

Designed resin

resinous acid value N=8.0

polyester resin weight W=259.3

number of functional groups in isophthalic acid f=2

reaction percentage of later charged isophthalic acid P=90%

mole % of carboxyl groups derived from isophthalic acid in the total carboxyl groups capable of developing resinous acid value x=75

Using the abovesaid equation with this data b₁ =0.139 mole (23.05 parts) was obtained.

Into a reaction tank equipped with a heating device, a stirrer, a reflux condenser, a water separator, a fractional tower and a thermometer, were placed the abovesaid six materials and the mixture was heated. At this time, isophthalic acid was used in an amount of 43.43 parts (66.48-23.05=43.43 parts). At the stage when the materials were fused out, stirring was started and heating was continued until the tank temperature reached 230° C. However, from 160° C. to 230° C., the temperature was raised at a constant rate in 3 hours. The formed condensation water was distilled out of the system. When the temperature reached to 230° C., the tank mixture was maintained at the same temperature for 1 hour and then 5 parts of xylene (refluxing solvent) were gradually added and a condensation reaction was further continued in the presence of said solvent. The reaction was stopped at the stage when the resinous acid value reached 2.0 calculated by the equation: ##EQU4## and the tank was allowed to cool to 100° C. to obtain a polyester prepolymer A-I. Next, 23.05 parts (0.139 mole) of isophthalic acid were placed in the tank and the tank temperature was raised to 210° C. At this time, from 190° C. to 210° C., said temperature was raised at a constant speed in 1 hour and the this condensation water formed was distilled out of the system. When the tank temperature reached 210° C., the tank was maintained at this temperature to continue the reaction. The said reaction was stopped at the stage when the resinous acid value reached 8.0 and the reaction mixture was allowed to cool. After cooling, 106.1 parts of xylene were added to obtain an acid controlled modified polyester resin solution A, the carboxyl groups capable of developing the resinous value for said resin being controlled in kind. This solution A had a non-volatile content of 70.1%, a varnish viscosity (Gardner viscosity, 25° C.) of Z₁, and a resinous acid value of 8.1.

Using pyridine solutions of the thus obtained polyester prepolymer A-I and of the acid controlled modified polyester resin solution A, non-aqueous potentiometric titration was carried out with a titration reagent of n-tetrabutyl ammonium hydroxide (TBAH) and the titration curves were shown in FIG. 1.

As clearly known from the drawing, the titration midpoint potential (R) of polyester prepolymer A-1 (2) is -400 mV which agrees with the the titration midpoint potential of polyester resin derived from an acid component of hexahydrophthalic anhydride alone as shown in Table 1. It was thus confirmed that the carboxyl groups, in which the resinous acid value of the 2.0 of polyester prepolymer A-1 was developed, were all derived from the hexahydrophthalic anhydride used. However, in the titration curve (1) of acid controlled modified polyester resin solution (A), there are 2 inflection points and the titration midpoint potentials (P.Q) are -313 mV and -405 mV, respectively, which are well in accord with the titration midpoint potentials of -310 mV and -400 mV for the polyester resins whose acid components are isophthalic acid alone and hexahydrophthalic anhydride alone as shown in Table 1. Therefore, the carboxyl groups which contribute to the development of the resinous acid value 8.1 of the acid controlled modified polyester resin solution A, are derived from both isophthalic acid and hexahydrophthalic anhydride, the equivalent ratio of these acids being 75/25. Thus, it was confirmed that the type of carboxyl groups capable of developing the resinous acid value were surely controlled as indicated under the passage "designed resin" by x=75%.

TABLE 1

Titration midpoint potentials for various carboxylic acids at the stage capable of developing a resinous acid value

    ______________________________________                                                   electric potential (mV)                                              ______________________________________                                         HHPA        -400                                                               AdA         -390                                                               sebacic acid                                                                               -420                                                               PAn         -290                                                               IPHA        -310                                                               TMAn        -240                                                               ______________________________________                                          HHPA . . . hexahydrophthalic anhydride                                         AdA . . . adipic acid                                                          PAn . . . phthalic anhydride                                                   lPHA . . . isophthalic acid                                                    TMAn . . . trimellitic anhydride                                         

EXAMPLES 2 TO 5

Based on the resinous compositions shown in Table 2, acid controlled modified polyester resin solutions B to E were prepared according to the procedures of Example 1. The characteristic values of these varnishes are shown in Table 2.

EXAMPLES 6 to 7

Based on the resinous compositions given in Table 2, modified polyester resin solutions F and G (whose resins were not acid controlled) were prepared by a conventional polyesterification, for comparison's sake. The characteristic values of these varnishes are also shown in Table 2.

                                      TABLE 2                                      __________________________________________________________________________     Example No.   1    2    3    4    5    6   7                                   resinous solution                                                                            A    B    C    D    E    F   G                                   __________________________________________________________________________     composition of polyester                                                       prepolymer                                                                     hexahydrophthalic anhydride                                                                  77.4 71.98                                                                               75.85                                                                               30.96                                                                               96.44                                                                               77.4                                                                               108.36                                            (0.5)                                                                               (0.465)                                                                             (0.490)                                                                             (0.2)                                                                               (0.623)                                                                             (0.5)                                                                              (0.7)                               isophthalic acid                                                                             43.43                                                                               66.48                                                                               66.48                                                                               63.48     66.48                                                 (0.261)                                                                             (0.4)                                                                               (0.4)                                                                               (0.382)   (0.4)                                   adipic acid   14.62                                                                               14.62                                                                               14.62                                                                               14.62                                                                               49.86                                                                               14.62                                                                              49.86                                             (0.1)                                                                               (0.1)                                                                               (0.1)                                                                               (0.1)                                                                               (0.3)                                                                               (0.1)                                                                              (0.3)                               trimethylolpropane                                                                           25.61                                                                               25.61                                                                               25.61                                                                               25.17                                                                               46.70                                                                               25.61                                                                              46.70                               neopentylglycol                                                                              52.67                                                                               52.67                                                                               52.67                                                                               70.32                                                                               30.82                                                                               52.67                                                                              30.82                               1,6-hexanediol                                                                               55.40                                                                               55.40                                                                               55.40                                                                               60.90                                                                               64.83                                                                               55.40                                                                              64.83                               composition of later charging                                                  polycarboxylic acid (B)                                                        phthalic anhydride 5.19           11.44                                                           (0.035)        (0.077)                                      isophthalic acid                                                                             23.05          52.86                                                           (0.139)        (0.318)                                           trimellitic anhydride   1.97                                                                           (0.010)                                                designed resin                                                                 weight W of polyester resin                                                                  259.30                                                                              259.07                                                                              259.72                                                                              254.88                                                                              259.27                                                                              259.30                                                                             259.75                              resinous acid value N                                                                        8.0  8.0  8.0  8.0  20.0 8.0 20.0                                number of functional groups                                                                  2    2    3    2    2                                            in later charging (B) f                                                        reaction % P of said (B)                                                                     90   60   40   95   70                                           mole % of (B) in carboxyl                                                                    75   75   50   87.5 50                                           groups developing resinous                                                     acid value x                                                                   characteristic value of                                                        varnish                                                                        varnish viscosity                                                                            Z.sub.1                                                                             Z-Z.sub.1                                                                           Z.sub.2 -Z.sub.3                                                                    Z.sub.3                                                                             Y    Z-Z.sub.1                                                                          Y-Z                                 final resinous acid value                                                                    8.1  7.8  8.2  7.9  19.8 8.3 19.6                                non-volatile content (%)                                                                     70.1 69.6 70.5 70.0 70.3 69.6                                                                               70.3                                __________________________________________________________________________      () indicates moles                                                       

EXAMPLE 8

Using the acid controlled modified polyester resin solution A obtained in the aforesaid Example 1 and following the prescriptions as given in Table 3, 4 and 5, dispersion pastes of White, Red ion oxide, Cyanine blue and Anthraquinone Red colors were prepared.

                  TABLE 3                                                          ______________________________________                                         formulation of White colored dispersion                                        ______________________________________                                         titanium white (Note 2)                                                                              60        parts                                          acid controlled modified polyester                                                                   25                                                       resin solution A                                                               Solvesso 100 (Note 3) 15                                                       dispersing agent (Note 4)                                                                            0.05                                                                           100.05                                                   ______________________________________                                    

                  TABLE 4                                                          ______________________________________                                         formulation of Red ion oxide dispersion                                        ______________________________________                                         red ion oxide (Note 5)                                                                               50        parts                                          acid controlled modified polyester                                                                   30                                                       resin solution A                                                               Solvesso 100          20                                                       dispersing agent      0.05                                                                           100.05                                                   ______________________________________                                    

                  TABLE 5                                                          ______________________________________                                         formulation of cyanine blue dispersion                                         ______________________________________                                         cyanine blue (Note 6) 20                                                       acid controlled modified polyester                                                                   56                                                       resin solution A                                                               Solvesso 100          30                                                       dispersing agent      0.05                                                                           100.05                                                   ______________________________________                                    

                  TABLE 6                                                          ______________________________________                                         formulation of anthraquinone red dispersion                                    ______________________________________                                         anthraquinone red (Note 7)                                                                           16                                                       acid controlled modified polyester                                                                   34                                                       resin solution A                                                               Solvesso 100          50                                                       dispersing agent      0.05                                                                           100.05                                                   ______________________________________                                          Note 2 . . . titanium R 5N manufactured by Sakai Chem. Co.                     Note 3 . . . mixed solvent manufactured by Esso Standard Petroleum Co.         Note 4 . . . KF69 10% solution, manufactured by Shinetsu Silicon K.K.          Note 5 . . . Tenyo Red Ion Oxide 501, manufactured by Tone Sangyo K.K.         Note 6 . . . Fastgen Blue 7003, manufactured by Dainippon Ink Co.              Note 7 . . . Chromophthal Red A3B, manufactured by CibaGeigy White and Re      colored coating compositions were then prepared with the above said            dispersions and following the prescriptions given below.                 

                  TABLE 7                                                          ______________________________________                                         formulation of white colored coating composition                               ______________________________________                                         white dispersion paste                                                                               100       parts                                          blue dispersion paste 0.2                                                      acid controlled modified polyester                                                                   60                                                       resin solution A                                                               melamine resin        32.2                                                     n-butanol             2                                                        triethylamine         0.2                                                      surface conditioner (Note 8)                                                                         0.4                                                                            195.1                                                    ______________________________________                                          Note 8 . . . Modaflow 50% solution Monsanto Chem. Co.                    

                  TABLE 8                                                          ______________________________________                                         formulation of red colored coating composition                                 ______________________________________                                         red dispersion paste  62        parts                                          red ion oxide dispersion paste                                                                       35                                                       white dispersion paste                                                                               3                                                        acid controlled modified polyester                                                                   115                                                      resin solution A                                                               melamine resin        57                                                       n-butanol             5                                                        triethylamine         0.5                                                      surface conditioner   0.5                                                                            278.0                                                    ______________________________________                                    

Each of the abovesaid coating compositions was diluted with a mixed solvent consisting of 10 parts of toluene, 20 parts of Solvesso 100, 50 parts of Solvesso 150 (mixed solvent manufactured by Esso Standard Petroleum Co.) and 20 parts of butyl acetate to adjust the viscosity of 23 seconds/No. 4 Ford Cup (20° C.). And the respective composition was applied by spray coating onto spc-1 dull steel plates previously treated with zinc phosphate, subjected to cationic electrodeposition and then coated with an inter-coating composition, the coating was, after standing for a defined period of time, baked at 140° C. for 30 minutes.

The gel fraction, the weather resistance and the film performance properties of the thus obtained coating are shown in the following Table 9. (As to the gel fraction, measurement was also made with the coating baked at 120° C. for 30 minutes).

EXAMPLES 9 TO 12

Using the acid controlled modified polyester resin solutions B, C, D and E obtained in Examples 2 to 5 and following the prescriptions given in Tables 3 to 6, primary colored dispersion pastes were prepared, and then white and red colored coating compositions were prepared according to the prescriptions given in the abovesaid Tables 7 and 8, except B, C, D and E were used as the acid controlled modified polyester resin solution. These coating compositions were applied onto steel plates as in Example 8 and the gel fraction, the weather resistance and film performance test results were shown in Table 9.

EXAMPLES 13 to 14 (Comparative Examples)

Using the modified polyester resin solutions F and G obtained in Examples 6 and 7 and following the prescriptions shown in Tables 3 to 6, the respective primary colored dispersion paste was prepared, and then white and red colored coating compositions were prepared according to the prescriptions given in Tables 7 and 8, except B, C, D and E were used as the acid controlled modified polyester resin solutions. These coating compositions were then applied to steel plates as in EXAMPLE 8 and the gel fraction, weather resistance and film performance test results were shown in Table 9.

    TABLE 9       Example No. 8 9 10 11 12 13 14 resin solution A B C D E F G color white r      ed white red white red white red white red white red white red        gel fraction (%)               baked at 120° C. 88 87 90 91 91      90 91 91 92 92 80 79 78 79 baked at 140° C. 94 94 95 94 96 95 96      95 96 97 86 84 88 89 finish. appearance ○ Δ ○      Δ ○ Δ ○ Δ ○ Δ ○      Δ ○ Δ (gloss,) (Note 10) 60° (mirror) gloss 93      85 92 86 93 87 93 86 91 86 93 86 92 85 (Note 11) pencil hardness H H H H      H H H H H H FH FH FH FH impact strength (cm) 35 35 30 35 35 35 35 35 35      35 35 30 35 35 DuPont type Φ = 1/2" 500 g acid resistance good good      good good good good good good good good some dis good some dis good      (Note 12)           colored  colored alkali resistance good good good      good good good good good good good discolor some dis discolor some dis      (Note 13)           blister color blister color interlaminar adhesion      0/100 0/100 0/100 0/100 0/100 0/100 0/100 0/100 0/100 0/100 0/100 0/100      0/100 0/100 (Note 14) accelerated weather resistance QUV 300H 60°      gloss 86 88 88 85 87 86 87 86 86 83 77 78 82 78 retention QUV 600H      60° gloss 78 81 82 75 78 79 79 80 79 76 71 69 75 73 retention      outdoor exposure 83 76 82 77 84 80 83 82 83 80 76 72 76 70 at Okinawa      60° gloss after 18 months waxing resistance -- ○ --      ○ -- ○ -- ○ -- ○ -- ○ -- ○      after 18 months (Note 15)      Test method:      Note 9:      Gel fraction . . . Sample specimen of a baked coating was subjected to      solvent extraction with acetone/methanol = 1/1 (weight), using a      Soxhletextractor, at 70° C. for 5 hours, and the extract was dried      at 120° C. for 30 minutes in a drier, and then cooled in a      dessicator. The extract was weighed and the gel fraction was calculated      from the said result.      Note 10:      Finishing appearance was evaluated by visual observation of gloss and on      the basis of the following criteria:      ⊚ . . . very good       ○  . . . good      Δ . . . slightly inferior      x . . . no good      Note 11:      60° (mirror) gloss 60° reflectance was measured by using a      Murakami type glossmeter GM3M      Note 12:      Acid resistance 5 ml of N/10 H.sub.2 SO.sub.4 was dropped in a glass      cylinder (inner diameter of 38 mm, height of 15 mm) placed on the coating      After leaving it to stand for 24 hours at 20° C., the coating was      washed with water and any occurrence of wrinkles, blisters and color      changes were observed.      Note 13:      Alkali resistance 5 ml of N/10 NaOH was dropped in a glass cylinder as      used in said Note 12, and after leaving to stand in a drier (55°      C.) for 4 hours and subsequently washing with water, and occurrence of      wrinkles, blisters and color changes were observed.      Note 14:      Interlaminar adhesion Onto a substrate, the coating composition obtained      in each of the Examples was applied and baked at 160° C. for 30      minutes. Thereafter, the same coating composition was spraycoated as a to      coat and baked at 140° C. for 30 minutes (2 coats with the same      coating composition). Thereafter, crosscuts with 2 mm width cut were made      with a razor and a peel test was performed with a cellophane tape. The      result was evaluated by the number of peeled out coatings in a 2 cm squar      each.      Note 15 Waxing resistance:      A small quantity of car wax (Soft 99 semikneaded type manufactured by      Nitto Chem. Co.) was taken on a white linen and rubbed against the coatin      intensely with the forefinger 10 times back and forth over a distance of      10 cm. An excess amount of wax remained on the coating was wiped out with      a fresh linen cloth and the coating surface was visually observed. The      result was evaluated from the extent of gloss down, abrasions and colorin      to the white linen cloth.       ○  . . . no gloss down and abrasions on the coating, and no      coloring to white linen      Δ . . . slight gloss down and abrasions, and some coloring to white      linen      x . . . considerable gloss down and abrasions, and marked coloring to      white linen

EXAMPLES 15 TO 17

Acid controlled modified polyester resin solutions H, I and J were prepared as in Example 1, following the prescriptions given in Table 10. The characteristic values of these varnishes are shown in Table 10.

EXAMPLES 18 TO 19

Using the acid controlled modified polyester resin solutions H and I and following the prescriptions given in Tables 3 to 6 of Example 8, the respective primary colored dispersion pastes were prepared, and thereafter, following the formulations shown in Tables 7 and 8, except for using H and I as the acid controlled modified polyester resin solutions, white colored and red colored coating compositions were prepared. These compositions were then applied as in Example 1, and the test results (gel fraction, weather resistance and film performance) were summarized in Table 11.

EXAMPLE 20 (Comparative Example)

Using the modified polyester resin solution J obtained in Example 17 and following the prescriptions shown in Tables 3 to 6 of Example 8, the respective primary colored dispersion pastes were prepared and thereafter, following the paint compositions given in Tables 7 and 8 (except for using the modified polyester resin solution J in place of the acid controlled modified polyester resin solution), white colored and red colored coating compositions were prepared. These compositions were then applied as in Example 1 and the test results (gel fraction, weather resistance and film performance) were shown in Table 11.

The test methods used and evaluation standards are as shown previously.

                  TABLE 10                                                         ______________________________________                                         Example No.     15        16      17                                           resin solution  H         I       J                                            ______________________________________                                         coconut oil     30.11     117.9   117.9                                        DMCD                                                                           DD-100                                                                         hexahydro phthalic                                                                             46.44     46.44   46.44                                        anhydride       (0.3)     (0.3)   (0.3)                                        isophthalic acid                                                                               91.11     83.1    116.34                                                       (0.55)    (0.5)                                                trimethylol propane                                                                            28.96     70.51   70.51                                        neopentylglycol 82.39     43.89   43.89                                        1,6-hexanediol  17.50     9.08    9.08                                         later charged   25.23     33.24   --                                           isophthalic acid (B)                                                                           (0.15)    (0.2)                                                predetermined value                                                            for polyester                                                                  resin weight W  283.9     370.5   370.5                                        resnous acid value N                                                                           8.0       8.0     8.0                                          later charged (B)                                                                              2         2                                                    number of functional                                                           groups f                                                                       reaction % P    90.0      90.0                                                 B mole % occupied                                                                              75        75                                                   in carboxyl groups                                                             which develop resinous                                                         acid value x                                                                   varnish characteristics                                                        viscosity       Y-Z       W-X     X                                            resinous acid value                                                                            7.9       7.8     8.1                                          non-volatile %  70.2      70.5    70.2                                         Gel fraction %                                                                 baked at 120° C.                                                                        88        88      78                                           baked at 140° C.                                                                        94        94      86                                           ______________________________________                                          () indicates mole                                                        

                                      TABLE 11                                     __________________________________________________________________________     Example No. 18       19       20                                               resin solution                                                                             H        I        J                                                color       white                                                                              red  white                                                                              red  white                                                                              red                                          __________________________________________________________________________     gel fraction (%)                                                               baked at 120° C.                                                                    89  88   90  88   74  77                                           baked at 140° C.                                                                    95  96   94  95   86  86                                           (Note 9)                                                                       finish. appearance                                                                         ○                                                                           Δ                                                                             ○                                                                           Δ                                                                             ○                                                                           Δ                                      (gloss,)                                                                       (Note 10)                                                                      60° (mirror) gloss                                                                  93  86   92  88   92  87                                           (Note 11)                                                                      pencil hardness                                                                            FH  FH   HB  HB   HB  HB                                           impact strength (cm)                                                                       35  35   40  40   40  40                                           DuPont type Φ = 1/2"                                                       500 g                                                                          acid resistance                                                                            good                                                                               good good                                                                               good **  **                                           (Note 12)                                                                      alkali resistance                                                                          good                                                                               good good                                                                               good *   **                                           (Note 13)                                                                      interlaminar adhesion                                                                      0/100                                                                              0/100                                                                               0/100                                                                              0/100                                                                               0/100                                                                              0/100                                        (Note 14)                                                                      accerlated weather                                                             resistance                                                                     QUV 300H 60° gloss                                                                  86  85   84  84   72  70                                           retention                                                                      QUV 600H 60° gloss                                                                  78  79   78  77   58  60                                           retention                                                                      outdoor exposure                                                                           84  82   82  80   69  66                                           at Okinawa                                                                     60° gloss after                                                         18 months                                                                      waxing resistance                                                                          --  ○                                                                            --  ○                                                                            --  Δ                                      after 18 months                                                                (Note 15)                                                                      __________________________________________________________________________       *discolored, blister                                                           **somewhat discolored                                                   

EXAMPLE 21

Into a reaction tank fitted with a heating device, a stirrer, a reflux condenser, a water separator, a fractional tower and a thermometer, were placed 77.4 parts of hexahydrophthalic anhydride, 22.6 parts of trimethylol ethane, 22.4 parts of hydroxy pivalic acid neopentyl glycol ester (HPN), 56.1 parts of neopentyl glycol, 23.9 parts of Cardura E-10 (trademark of Shell Chem. Co., glycidyl compound), and 0.1 part of dibutyl tin oxide, and the mixture was heated. At the stage when the charged materials were fused out, stirring was started and heating was continued until the tank temperature reached 230° C. However, from 180° C. to 230° C., the temperature was raised at a constant rate in 3 hours.

While removing the formed water out of the system, the tank mixture was reacted at 230° C. until the resinous acid value reached 2.0 and thereafter allowed to cool to 80° C. The mixture was then added with 55.4 parts of isophthalic acid and heated to 210° C. At this time, from 190° C. to 210° C., the temperature was raised at a constant rate in 2 hours.

The mixture was reacted, while removing the formed water, at 210° C. until the resinous acid value reached 10.0, allowed to cool and then diluted with 102 parts of xylene to obtain a resinous solution K having a non-volatile content of 69.8% and a varnish viscosity (Gardner viscosity, 25° C.) of X-Y.

A non-aqueous potentiometric titration was carried out by using pyridine as a solvent and n-tetra butyl ammonium hydroxide (methanol/benzene=1/10 solution) as a titration reagent and it was confirmed that there were 2 inflection points in the titration curve with the titration midpoint potentials of -300 mV and -400 mV.

They are well in accord with the titration midpoint potentials for the polyester resins whose acid components are isophthalic acid alone and hexahydrophthalic anhydride alone, respectively. From said analysis, it was also confirmed that 80 mole % of the carboxyl groups capable of developing resinous acid value were derived from isophthalic acid used.

EXAMPLE 22

27.7 parts of hexahydrophthalic anhydride, 19.8 parts of isophthalic acid, 11.0 parts of trimethylol ethane, 8.2 parts of HPN, 20.6 parts of neopentyl glycol, 9.3 parts of Cardura E-10 and 0.02 part of dibutyl tin oxide were reacted as in Example 15. After cooling to 80° C., 1.7 parts of phthalic acid were added and the mixture was reacted at 150° C. for 1 hour and then diluted with 30 parts of xylene to obtain a resinous solution L having a nonvolatile content of 75.1, a viscosity (Gardner viscosity, 25° C.) of X-Y.

From the non-aqueous potentiometric titration analysis showing the titration midpoint potential of -290 mV, it was confirmed that 80 mole % of the carboxyl groups capable of developing resinous acid value were derived from phthalic anhydride in the formed resin.

EXAMPLES 23 AND 24

Using the polyester resin solutions K and L obtained in Examples 21 and 22, and following the prescriptions shown below, clear coating compositions were prepared.

                  TABLE 12                                                         ______________________________________                                         Formulation of clear coating composition                                       ______________________________________                                         polyester resin solution (on solid basis)                                                               70      parts                                         U-van 128 (butylated melamine, trade mark                                                               30      parts                                         of Mitsui Tohatsu)                                                             (on solid basis)                                                                                        100     parts                                         ______________________________________                                    

Thus obtained compositions each was applied by using a doctor blade, on a polypropylene plate in 4 mil thickness. The coated plates were then baked at 140° C. or 100° C. in hot air drier, for 30 minutes and after cooling, the formed films were peeled out of the plates and gel fraction of the respect film was evaluated as in Example 8. The test results are shown in Table 13.

                  TABLE 13                                                         ______________________________________                                         Gel fraction %                                                                 Example                23    24                                                polyester resin solution                                                                              K     L                                                 ______________________________________                                         baking temperature °C.                                                  100                    60    68                                                120                    80    85                                                140                    94    95                                                low temp. curing property                                                                             ○                                                                             ○                                          judged from the Gel fraction %                                                 ______________________________________                                    

EXAMPLES 25 AND 26

Using the polyester resin solutions K and L and following the prescription shown below, white colored dispersion pastes were prepared.

                  TABLE 14                                                         ______________________________________                                         Formulation of white colored dispersion paste                                  ______________________________________                                         polyester resin solution (on solid basis)                                                             59.5     parts                                          melamine resin (on solid basis)                                                                       19.4                                                    titanium white (Note 1)                                                                               60.0                                                    triethylamine          0.2                                                     ______________________________________                                          (Note 1: titanium R5N manufactured by Sakai Chem. Co.)                         Each of the abovesaid dispersion paste was diluted with a mixed solvent o      10 parts of toluene, 20 parts of Solvesso 100 (trademark of Esso               Standard), 50 parts of Solvesso 150 (trademark of Esso Standard, mixed         solvent) and 20 parts of butyl acetate to the viscosity of 23 seconds/No.      4 Ford Cup (20° C.).                                              

The respective composition was applied onto a spc-1 dull steel plate previously treated with zinc phosphate, subjected to a cationic electrodeposition and then coated with an inter-coating composition, and thus formed coating was, after standing for a defined period of time, baked at 140° C. for 30 minutes. The film performance properties of thus obtained coatings were evaluated as in Example 8 and the test results were shown in Table 15.

                  TABLE 15                                                         ______________________________________                                         Example No.          25      26                                                polyester resin solution                                                                            K       L                                                 ______________________________________                                         finishing appearance ⊚                                                                       ○                                          60° (mirror) gloss                                                                           96      92                                                pencil hardness      H       H                                                 acid resistance      good    good                                              alkali resistance    good    good                                              impact strength (cm) 40      35                                                (DuPont type o = 1/2" 500 g)                                                   interlaminar adhesion                                                                               0/100   0/100                                             accelerated weather resistance                                                 QUV 300H 60° gloss retention                                                                 88      84                                                QUV 600H 60° gloss retention.                                                                78      73                                                ______________________________________                                    

Possibility of industrial use

As mentioned hereinabove, the present resinous composition can afford excellent coating, when used as a resinous vehicle in a clear or colored coating composition and possesses, in particular, good weather resistance, mechanical properties and interlaminar adhesion, and especially exhibits excellent curing properties. This makes the coating composition especially suitable as a top coat for automobile bodies and the like. 

What is claimed is:
 1. A resinous composition for a coating composition to be used as a top coat for automobile bodies, comprising 60 to 90% by weight of an acid controlled modified polyester resin and 40 to 10% by weight of an aminoformaldehyde resin etherified with a monohydric alcohol having 1 to 4 carbon atoms, said polyester resin being composed of(1) an alcohol component consisting of(A) 20 to 64% by weight of at least one diol selected from the group consisting of neopentyl glycol and hydroxy pivalic acid neopentyl glycol ester, (B) 14 to 34% by weight of a triol selected from the group consisting of trimethylol propane and trimethylol ethane and (C) 0 to 66% by weight of a polyhydric alcohol other than said (A) and (B), and (2) an acid component consisting of(D) a mole % of saturated alicyclic polycarboxylic acid, (E) b mole % of polycarboxylic acid which will give, at a state capable of developing a resinous acid value, a titration midpoint potential in non-aqueous potentiometric titration of more than -350 mV, and (F) c mole % of at least one acid selected from the group consisting of polycaroxylic acids other than said (D) and (E), and monocarboxylic acid, wherein a is 10 to 80 and b+c is 90 to 20, 10 to 100 mole % of the carboxyl groups capable of developing a resinous acid value for the polyester resin derived from said (E) acid.
 2. A composition according to claim 1 where the other polyhydric alcohol (C) is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,6-hexane diol, 1,5-pentane diol, 2,5-hexane diol, glycerine, pentaerythritol, diglycerine, sorbitol, and 1,4-cyclohexane dimethanol.
 3. A composition according to claim 1 in which the diol (A) is neopentyl glycol.
 4. A composition according to claim 1 in which the alcohol component consist of (A) neopentyl glycol, (B) trimethylol propane and (C) 1,6-hexane diol. 